1. Field
Embodiments of the present invention relate to bushing and spacer systems for use with hammer mills. More particularly, embodiments of the present invention relate to bushings configured to be mounted on a hammer rod and to receive hammers such that the bushings support the hammers, shield the rod from contact with the hammers, and separate the hammers one from another.
2. Related Art
Hammer mills, sometimes referred to as impact grinders, are well known in the art and are used for grinding or comminuting materials such as scrap metal, forestry and agricultural materials, minerals, recycling materials, and food components such as grain. A typical hammer mill comprises a rotor mounted on a rotor shaft that is driven by a motor. The rotor includes a series of rotor discs spaced axially along the rotor shaft, and a plurality of hammer rods mounted on the rotor discs and extending the length of the rotor. The hammer rods are spaced radially outwardly from the rotor shaft and spaced circumferentially from one another. A plurality of free-swinging “hammers,” typically planar, elongated metal pieces, are mounted on the rods such that when the motor induces rotational movement in the rotor, the hammers extend radially outwardly from the rotor responsive to the centrifugal force associated with the rotation of the rotor.
An enclosure surrounds the rotor and includes a material inlet typically located at a top of the enclosure for allowing material to be dropped into the hammer mill for grinding. The enclosure may further comprise a perforated wall at least partially defining a grinding chamber, wherein the perforated wall enhances the grinding process and filters material particles from the grinding chamber as they are sufficiently reduced in size.
Because the hammers rotate and otherwise move on the rods, both the hammers and rods tend to wear over time at the points of contact. Over time this wearing tends to cause the hammer apertures to elongate and the rods to develop grooves. Such wearing can cause the hammers to extend radially outwardly relative to the rotor which can, in turn, cause the hammers to come into contact with the enclosure, potentially damaging both the hammers and the enclosure if not corrected.
Accordingly, there is a need for an improved hammer mill which overcomes the limitations described above.